public class ReplaceCheck
{
   /**
      A method to replace letters as follows:
      the letter e becomes 3, the letter i becomes 1,
      the letter l becomes 7, and the letter o becomes 0.
      @param str a string
      @return the string with the characters replaced
   */
   public static String replace(String str)
   {
      String result = "";
      for(int i = 0; i < str.length(); i++)
      {
         char a = str.charAt(i);
         String b = "";
         switch(a)
         {
            case 'e': result += '3';break;
            case 'i': result += '1';break;
            case 'l': result += '7';break;
            case 'o': result += '0';break;
            default: result += a;
         }
      }
      return result;
   }
}